Method for emission control for spark ignition engines

ABSTRACT

Method and apparatus for operating internal combustion spark ignition engines in a manner to reduce the harmful constituents of the exhaust of the engine. The engine is operated, except during peak power requirement, with very lean air-fuel mixtures. The loss of power generally accompanied by lean air-fuel mixtures due to slow burning is avoided by supplying turbulence of proper intensity to the burning mixture. The turbulence is supplied by constructing a combustion chamber divided into main and auxiliary sections joined by an orifice. By selecting the proper orifice size and the proper ratio of the volumes of the main and auxiliary sections sufficient turbulence can be provided to burn the lean air-fuel mixture within normal crank angles.

v United States Patent 11 1 1111 3,776,212

Karlowitz Dec. 4, 1973 [54] METHOD FOR EMISSION CONTROL FOR 3,283,75111/1966 Goossak et a1. 123/32 SPARK IGNITION ENGINES 3,304,922 2/1967Hideg 123/32 2,173,081 9/1939 Barker 123/191 SP Inventor: BelaKarlowitz, 1510 Scenery Ridge 1,825,658 10/1931 Dumanois.. 123/32 E Dr.,Pittsburgh, Pa. 15241 OTHER PUBLICATIONS 1 1 Filed: 22, 1970 SAE Journal11-63 pages 60-63. [21] Appl. No.: 83,163

Primary Examiner -Laurence M. Goodndge Related Appliealien DateAttorney-Webb, Burden, Robinson & Webb [63] Continuation of Ser. No.798,716, Feb. 12, 1964,

abandoned. 5 7 ABSTRACT Method and apparatus for operating internalcombus- [52] 123,191 123,32 123,32 tion spark ignition engines in amanner to reduce the 123/32 123/30 [23/32 C harmful constituents of theexhaust of the engine. The [51] Iltt. Cl. F02!) 19/00 engine isOperated, except during peak power require [58] Fleld of Search 123/32,32 ST, 32 SP, ment, i y lean air fue| mixtures The loss f 123/191, 32 32E power generally accompanied by lean air-fuel mixtures due to slowburning is'avoided by supplying tur- [56] Reerences C'ted bulence ofproper intensity to the burning mixture.

UNITED STATES PATENTS The turbulence is supplied by constructing acombus- 3,406,667 10/1968 Evans 123 143 A ti chamber divided into a aauxiliary sections 2,173,081 9/1939 Barkeij 123/191 SP joined by anorifice. By selecting the proper orifice 2,121,920 6/1933 M y--- 123/32ST size and the proper ratio of the volumes of the main 2,153,618 4/1939Fischer 123/32 and auxiliary sections sufficient turbulence can be21156-665 5/1939 Mallorym 123/32 ST provided to burn the lean air-fuelmixture within nor- 2,753,852 7/1956 Beller 123/32 mal Crank angles2,758,576 8/1956 Schlarnann 123/32 ST 3,092,088 6/1963 Goossak et al...123/32 UX 16 Claims, 1 Drawing I 8B PMENIEDME 4:915 3.776.212

//V VE/VTOR. Bela Kar/o vi): 5)

HIS A TTORNE Y5 METHOD FOR EMISSION CONTROL FOR SPARK IGNITION ENGINESThis application is a continuation of Ser. No. 798,716, filed Feb. 12,1969, now abandoned.

BACKGROUND The permissible limits of the emissions and the ultimategoals which go beyond the legal limits are shown in the followingtabulation:

HC CO NO pp pp Present standard 275 1.5 350 1970 standard 180 1.0 350Ultimate Objectives 65 0.5 175 These values are the averages measured ina standardized test program simulating city driving conditions.

To reduce the average CO content of the exhaust gas below 0.5 percent itis sufficient to operate the engine with an air-fuel ratio of about 16.Such slightly lean mixtures burn quite rapidly in present day enginesand are satisfactory except when peak power is required. This usepresents no difficulties if the intake system can deliver a uniformmixture to the cylinders. However, the reduction of the NO content ofthe exhaust to acceptable levels requires much leaner mixtures, forexample mixtures with air-fuel ratio of about 18 to 20.

In present spark ignition engines combustion of the charge in thecylinder requires about 50 to 60 of crank angle for faster burningmixtures, and about 90 for slower burning lean mixtures with an adr-fuelratio in excess of about 16. The long combustion time causes powerlosses because of the motion of the piston during the combustion period.For very lean mixtures torque and efficiency of the engine decrease byan unacceptable to 20 percent or more and the engine performance becomessluggish. The long combustion time also allows sufficient time forself-ignition of part of the highly compressed charge (knockingcombustion) unless the fuel possesses sufficient anti-knock additiveswhich may also be pollutants.

According to this invention, combustion is sufficiently accelerated sothat the engines can operate most of the time with very lean mixtureswithout loss of power. However, during peak power operation nearstoichiometric mixture is required unless the size of the engine isgreatly enlarged. Since peak power operation contributes only a fewpercent of the total engine exhaust, the use of near stoichiometricmixtures during peak power operation is permissible without seriousoverall effect on the emissions.

Operation of engines according to this invention with very lean mixturesbecomes possible without loss of power or efficiency by generating theproper intensity of turbulence in the combustion chamber during thecombustion period. Thereby combustion is so accelerated that it can becompleted within a 60 to 30 crank angle. The intensity of turbulencerequired for this purpose is less, but not very much less, than theturbulence intensity which the flame can tolerate without beingquenched.

It is known that the time required for combustion is strongly affectedby turbulence. Indeed, the present day spark ignition engines make gooduse of turbulence. Various schemes are used to generate turbulence bythe displacement of the charge by the piston or by the inflow velocityof the charge. However, because turbulence decays very rapidly for thepurposes of this invention, it must be generated when it is required.

Turbulence has an additional beneficial effect besides shortening thetime of combustion. There is a thin layer of combustible mixture next tothe walls of the combustion chamber and in the crevices between thepiston and cylinder wall, which is not consumed by the passing flamebecause the flame is quenched in the vicinity of the wall. Sufficientturbulence will mix this combustible film with the burning; gas or hotcombustion products. The film is thereby ignited and burned. Thus, theamount of unburned hydrocarbons in the exhaust gas is substantiallyreduced. During peak power operation of spark ignition engines nearstoichiometric air-fuel mixtures are required. These mixtures generallymust contain anti-knock additives to prevent engine knock. However, bygenerating the proper intensity of turbulence, these mixtures can beburned rapidly enough to reduce or eliminate these additives. Hence, itis possible according to this invention to operate an internalcombustion spark ignition engine during both normal and peak powerperiods so the exhaust emissions contain little, if any, lead or otheranti-knock chemicals which are very undesirable pollutants.

THE INVENTION According to this invention an internal combustion sparkignition engine having at least one cylinder and piston defining acombustion chamber is operated at most conditions with very leanair-fuel mixtures, for example in excess of 18:1. The combustion chamberis divided into main and auxiliary sections with an orificetherebetween. During operation, the combustible mix is fed to thecylinder in any of the conventional ways. The combustible mixture isthen compressed by the movement of the piston. Part of the mixture isforced through the orifice into the auxiliary chamber creating greatturbulence therein. The mixtureis then ignited with sparks of anelectrode (the timing of ignition being according to well knownprinciples). As will be more fully explained, the electrodes may belocated in the main section of the combustion chamber or in theauxiliary section. Due to the turbulence in the auxiliary section of thechamber the air-fuel mixtures burn very rapidly causing a rapid rise inpressure. The gases in the auxiliary section then rush through theorifice into the main section causing turbulence therein. The size ofthe orifice and the ratio of the volumes of the main and auxiliarysections are selected so that the combustion products rushing out of theauxiliary section provide sufficient turbulence to the main section tocause total burning within an acceptable crank angle, usually 60, yetnot such strong turbulence to quench the flame. The volume of theauxiliary section should be from 3 to 15 percent and preferably from 8to 12 percent of the compression volume in order to provide sufficientenergy for turbulence generation. The auxiliary section will typicallybe 10 percent by volume of the compression volume for the mostsatisfactory results. The orifice size is partially determined by theamount of turbulence required. The orifice size is also controlled bythe conditions necessary for passing a flame through an orifice. If, forexample, ignition is provided in the auxiliary section the orifice mustbe sufficiently large enough to allow the flame to pass out of theauxiliary section. On the other hand, if ignition is in the main sectionof the combustion chamber the orifice must be sufficiently large topermit a flame to pass into the auxiliary section. Engines operatedaccording to this invention burn very lean air-fuel mixtures withoutpower loss except during rapid acceleration at which timesstoichiometric mixtures must be used. The use of very lean mixtures andstrong turbulent mixing results in very low emission of NO, CO andunburned hydrocarbons in the engine exhaust.

Furthermore, engines operated according to this invention may burn fuelwith little, if any, anti-knock additives resulting in very lowundesirable emissions of lead or other anti-knock chemicals. In thiscase, the

size of the orifice andthe ratio of the volumes of the main andauxiliary sections are further selected to create turbulence ofsufficient intensity to burn stoichiometric air-fuel mixtures withinabout a 30 crank angle. One of the discoveries upon which this inventionis predicated is that an orifice size and a ratio of volumes between themain and auxiliary sections can be selected to satisfy the requirementsof normal operation on lean air-fuel mixtures and to satisfy therequirements of peak power operation on near stoichiometric air-fuelratios.

The drawing is a schematic section view of an internal combustion sparkignition cylinder and piston.

DETAILED DESCRIPTION In a spark ignition engine, the charge in thecylinder after compression consists of vaporized fuel mixed with air.The combustion reaction in such mixture occurs in a very thin combustionwave which propagates into the unburned mixture. Due to turbulence thiscombustion wave is wrinkled and very large combustion wave area ispacked into a small volume. The reaction rate per unit volume isproportional to the total area of the combustion wave, therefore, thechange is consumed in a short time interval by the turbulent flame.

THE INTENSITY OF TUBULENCE REQUIRED The combustion wave propagating in acombustible mixture is characterized by the propagation velocity of thewave, denoted as burning velocity S and by the thickness of thecombustion wave 17 The ratio of the se quantities (n /S is thecharacteristic time of the combustion wave (t Thickness of thecombustion wave and burning velocity are connected by the relationship.

1 )t/e, a S

where A heat conductivity of the unburned mixture 18 callcmC sec 0,,specific heat of the unburned mixture cal/gC a density of the unburnedmixture g/cm Turbulence is characterized by the root means square valueof the random fluctuating velocities, usually called the intensity ofturbulence, u, and by the average size of the random eddies called thescale of turbulence l. The ratio of these two quantities (l/u') is thecharacteristic time of turbulence (T).

Turbulent motion continually stretches the area of a randomly wrinkledcombustion wave existing in a turbulent combustible medium, whileburnout of the combustible mixture eliminates combustion wave area.Theoretical calculations and experience shows that the time required tocomplete combustion in a turbulent medium is approximately twelve timesthe characteristic time, that is,

Hence, the time required for combustion may be reduced by increasing theintensity of turbulence. On the other hand, the shortest permissibletime is limited by the requirement that the characteristic time ofturbulence shall not be shorter than the characteristic time of thecombustion wave. That is, the charactertistic number must be smallerthan a critical value, which is in the order of one. If thecharacteristic number approaches its critical value then the combustionwave breaks apart due to rapid stretching and the flame is quenched bythe combustible mixture.

EXAMPLE I Numerically in a typical engine with a compression ratio of10:1 operated on a very lean air-fuel mixture (A/F 20) the followingnumerical values may be assumed:

S 20 cm/sec 0,, 0.24 callgC A 0.6 X 10" ca.l/cmC sec Hence,

1 )t/c (r S (0.6 X l0")/(0.24 X 9.2 X 10 20) 0.136 X 10' cm Thecharacteristic time of the combustion wave, and the shortest permissiblecharacteristic time of turbulence is therefore t =(17 /S (0.136 X l0)/(20) 0.68 X 10 sec (l/u') minimum Operation of the engine with suchvery lean mixtures (A/F 20) becomes possible without power loss ifcombustion is accomplished within approximately 45 crank angle. At 3,000RPM the time interval available for combustion is A t 15/360) (60/3000)2.5 X 10 second The characteristic time of turbulence required tocomplete combustion in this time interval is T= At/l2 (2.5 X l0 /l2) 2.1X 10" sec Clearly, the required turbulence intensity is well below thepermissible limit. Therefore, it is possible to burn a very lean mixtureof A/F 20 within 45 crank angle, even at 3,000 RPM, if the proper amountof turbulence is introduced into the mixture.

EXAMPLE [I In the same engine referred to in Example I, burning a nearstoichiometric mixture with S, 40 cm/sec and 1;, 0.068 X 10 thecharacteristic time of the combustion wave is t "n /S, (0.068 X 10 /40)0.17 X 10" sec (l/u') min It is desirable to burn the nearstoichiometric mixtures during full power operation in approximately 30crank angle to reduce the anti-knock requirements of the fuel. At 3,000RPM the time interval available for combustion is At (30/360) (60/3000)1.66 X 10 second The required characteristic time of turbulence istherefore T.= At/l2 (1.66 X 10 )/(12) 1.4 X10 sec. This is less than thecharacteristic time of the combustion wave, therefore, the turbulenceintensity required to complete combustion in the desired short timeinterval is substantially below what the flame can safely tolerate.

ROUGH BURNING Fast combustion can cause engine roughness if the rate ofpressure rise exceeds 50 psi degree of crank. an-

gle. However, combustion of a stoichiometric mixture in an engine withcompression ratio within 30 crank angle would produce only about 44 psiper degree, if the development of pressure is smooth. Withturbulencegeneration by an independent mechanism, like the jet issuingfrom the pod, there will be a smooth pressure rise.

Furthermore, it is very likely that engine roughness depends not so muchon the rate of pressure rise than on the shape of the pressure curve.Slow decline of the burning rate during the latter part of thecombustion seems to be beneficial for smooth operation. As the jet fromthe auxiliary section ceases to operate when about half of the charge isconsumed, a slow decline in the burning rate is to be expected.

GENERATION OF TURBULENCE Turbulence is generated by feeding energy intolarge size eddies, which in turn drive smaller and smaller eddies. Insteady state, or quasi-steady state, the scale of turbulence, l, isdetermined by the geometry of the system and is. proportional to somecharacteristic dimension of the system. It may be assumed to beapproximately constant even though the intensity of turbulence, u, mayvary in wide limits.

The rate of energy absorption per unit mass of the turbulent medium isde l/ or also where e is the kinetic energy of turbulent motion per.unit mass of the medium and e is the rate of energy dissipation.Without continued energy input the kinetic energy of the turbulentmotion, 3(u' /2) is reduced by the factor l/e 0.367 in a time intervalof T= l/u'.This shows that at the veryshort characteristic timesrequired for rapid combustion, turbulence cannot be introduced into thecharge much ahead of the combustion period. Turbulence must be generatedwhen it is needed.

The energy absorption equation above also shows that in the case whereturbulence is sustained by continued energy input, the characteristictime varies inversely with the one-third power of the energy inputrate;.that is, the resulting characteristic time is not very sensitiveto the energy input rate. Large variation of the energy input rate willonly slightly affect the resulting characteristic time of turbulencewhich is required for combustion control. This circumstance is veryadvantageous,.because exact control of the rate of energy input intoturbulence generation is not possible under the variable operatingconditions of a piston engine.

Turbulent flamesthemselveslgenerate turbulence by the differential(acceleration of randomlymixed burned and unburned gas masses. Theintensity of turbulence generated by this mechanism is dependent on thegeometry of the confinement of the flame. In a piston engine thisprocess is manifested by the fact that stronger mixtures, which have alarger expansion ratio on combustion, burn faster than leaner mixtures.This effect plays an important part in the combustion process of presentday engines, however, it :is not strong enough to produce the desiredshorter combustion times.

One way to generate the required strong turbulence during the combustionprocess is to have a small auxiliary section, chamber, or combustion podin communication with the main combustion chamber of the cylinderthrough an orifice.

Referring now to FIG. 1, the combustion chamber is shown defined bycylinder walls 1, cylinder head 2 and a piston 3. The section is suchthat intake and exhaust valves are not shown. The main section 4 of thecombustion chamber is connected with an auxiliarysection orcombustionpod 5 by an orifice 6. Ignition electrodes (spark plugs) areshown in alternate positions. (Of course, only one electrode is used ineach combustion chamber.) Electrode 8A is positioned to ignite acombustible mixture in the main combustion section. In this instance,the electrode is placed adjacent the orifice 6.

. Electrode 8B is shown positioned within the combustion pod.

During the compression stroke fresh combustible mixture is pushed intothe pod through the orifice. The velocity through the orifice can becalculated from the following formula:

p i/Va) where U Flow velocity through the critic U Piston speed A, Areaof piston A Area of orifice V, Volume of pod (constant) V, Cylindervolume above the piston (variable) The kinetic energy of the streamentering the pod is rapidly converted into turbulence, sothat at thetime of ignition by the spark, which may be in the main section of thecombustion chamber of the cylinder or in the pod, the mixture in the podis highly turbulent motion. If the spark is in the main section of thecombustion chamber, that is, outside of the pod, the flame is carriedinto the pod by the inflowing stream of burning mixture. In the highlyturbulent mixture in the combustion is very rapid. Shortly afterignition the pressure in the pod exceeds the pressure in the cylinderand a high velocity burning jet is ejected into the cornbusion chamber.This jet spreads the flame out over the volume of the combustion chamberand generates the turbulence necessary for the rapid completion ofcombustion. During the fast pressure rise in the combustion chamber thepressure differential across the orifice is again reversed, and the podacts as a damper against pressure fluctuations. During the expansionstroke and at the time of the opening of the exhaust valve, the pressurein the pod is higher than in the cylinder and again a jet issues fromthe orifice. This jet entrains and mixes the contents of the cylinderand facilitates thereby the burning of the quenched fractions of themixtures.

The total energy available for turbulence generation is proportional tothe volume of the pod and to the expansion ratio of the burned andunburned gas. lt is, therefore, larger for richer mixtures than forleaner mixtures. This is advantageous because richer mixtures must burnfaster to avoid self-ignition and engine knock.

The rate at which the energy for turbulence generation is delivered isdependent on the initial turbulence intensity in the pod. The rate ofenergy delivery and turbulence intensity therefore increases withincreasing engine RPM, as required.

The required volume of the pod may be estimated from the total energyrequirement for turbulence generation over the entire'combustion period.

EXAMPLE III For example, in an engine with 10:1 compression ratio, 3.88inches bore, 3.0 inches stroke operating with a lean mixture (A/F 20) at3000 RPM and allowing 45 crank angle, for combustion the time intervalfor combustion is At 2.5 X

10 sec the required characteristic time of turbulence T 2.1 X 10 sec thescale of turbulence l 0.2 cm

the required intensity of turbulence u 1000 cm/sec the rate of turbulentenergy dissipation e 0.71

x10 erg/g sec the mass of the charge in the cylinder M 0.7

gram

the total energy required to maintain the turbulence level duringcombustion Q 125 X 10 erg' At U 26,000 cm/sec jet velocity (a typicalvelocity) the total mass flow required of the jet becomes G 0.036 gram,which is 5 percent of the mass of the charge in the cylinder. Only aboutone-half of the gas contained in the pod can escape before the pressurein the pod and in the cylinder are equalized. The required volume of thepod is therefore about percent of the compression volume, or 6 cm. Theorifice area is calculated from the volume flow rate and the assumedvelocity of the jet. This gives an area of A 0.1 cm and with a flowcoefficient of 0.5 an orifice diameter of 0.5

For a given pod volume and orifice area the actual velocity of the jet,and the energy available for turbulence generation, will depend on therate of combustion in he pod. It is not possible to predict exactly theburning rate in the However, for every engine type the jet velocity andthe intensity of turbulence generated by the jet can be adjustedexperimentally by variation of the orifice size. A small orificeproduces higher inflow velocity into the pod and, therefore, fastercombustion. It also increases the velocity of the outflowing jet. Largerorifice reduces the burning rate in the pod and also the velocity of thejet. By proper adjustment of the orifice area it is possible to generatethe turbulence intensity which is sufficient for the desired shortcombustion time of the charge, but which is safely below the permissiblelimit.

At lower engine speeds, the flow velocities, burning rates, turbulenceintensity, etc. change approximately linearly with the RPM. Therefore,the crank angle required for combustion remains approximately constant.

EXAMPLE 1v Operating the same engine described in Example ill with astoichiometric mixture with S, 40 cm/sec at 5 3,000 RPM and allowing 30crank angle for combustion 4 At 1.66 X 10 sec T= 1.4 X 10" sec 10 u1,400 cm/sec e=2 X 10 erg/g sec Q 230 X 10" erg U 32,000 cm/sec (the jetvelocity is higher than for lean mixtures because of higher temperaturerise PASSING THE FLAME THROUGH THE OR IFICE The diameter of the orificemust be such that if the spark is in the compression space of thecylinder the flame can pass through the orifice into the pod at the jetvelocity which is generated by the compression stroke of the piston.Conversely, if the spark is in the pod, the orifice diameter must belarge enough to allow the flame to pass through the orifice at the jetvelocity generated by combustion of the mixture contained in the pod.

Under static conditions, that is, where there is no flow through anorifice, a flame can propagate through an opening if the diameter of theopening is larger than the quenching distance, which is a characteristicproperty of the combustible mixture. The quenching distance instoichiometric air-fuel mixtures is quite small even at atmosphericpressure and it is inversely proportional to the absolute pressure. Forexample, for stoichiometric propane-air mixtures the quenching distanceis 0.19 cm at atmospheric pressure. Consequently, under staticconditions flames can pass through very small openings particularly athigh pressures.

The conditions for the passage of a flame are very different if apressure differential exists across the orifice by which a jet isproduced. In this case the flame can move only wit the flow and notagainst the flow. Furthermore, the flame must pass through the region ofhigh turbulence intensity produced by the jet. The cri- 55 terion forthe survival of the flame is the same as in any other highly turbulentmedium, that is, the characteristic time of the combustion wave, m/Smust be smaller than the characteristic time of turbulence, T= l/u'. Inthe critical region where the laminar core of the jet flow becomesentirely turbulent the characteristic time of turbulence generated bythe jet is T a(d,,/U,,) where d is the orifice diameter U, is the flowvelocity at the orifice a is a numerical factor in the order of l to 2,the

value of which is dependent on the flow conditions v around the jet.

Therefore, the orifice size is limited by the following equation:

For the case where ignition is in the main section of the combustionchamber and the flame must be carried into the auxiliary chamber thevelocity of the jet carrying the flame can be calculated from theformula described above, that is EXAMPLE V In an engine with a 3 inchstroke, :1 compression ratio, at 3,000 RPM and 20 BTDC U 415 cm/sec V 78cm V 6 cm (pod volume) A,, 76 cm MIXING DURING EXPANSION During theexpansion stroke the pressure in the pod is always somewhat above thepressure in the cylinder. The jet which issues from the pod mixes. thecontents of the cylinder. Thereby the cold unburned fractions of thecharge are mixed with the hot combustion products and burned. Thevelocity of the jet issuing from the pod is again calculated from theformula U: p v (VI/V2) For example, at 3,000 RPM and 90 after top deadcenter the velocity of the jet is 8,000 cm/sec. Later, when the exhaustvalve opens and the pressure in the cylinder drops rapidly, the jetvelocity approaches sound velocity for a short time. If the engine isoperated with lean mixtures, and never with mixtures richer thanstoichiometric, it is to be expected that the thorough mixing of thegases in the cylinder during the expansion and exhaust phase by the jetwill remove the unburned hydrocarbons from the exhaust almost entirely.

Having thus described my invention with the particularity required bythe patent law, what is desired to be protected by Letters Patent is setforth in the following claims.

What I claim as my invention is:

1. A method of operating an internal combustion spark ignition enginehaving at least one cylinder and reciprocating piston therein defining acombustion chamber, said combustion chamber divided into main andauxiliary sections, said auxiliary section being in communication onlywith said main section, there being an orifice between the main andauxiliary section sized to pass a flame and promote turbulence such thatthe harmful exhaust emissions including CO, NO and unburned hydrocarbonsare substantially reduced comprising the steps for,

A. introducing only a very lean combustible mixture having an air-fuelratio of at least 18:1 only to the main section of the combustionchamber;

B. compressing the combustible mixture in the main section'of thecombustion chamber andthereby forcing part of the mixture through theorifice into the auxiliary section creating great turbulence therein;

C. igniting the combustible mixture within the combustion chamber from asingle ignition source:

D. causing a very rapid rise in pressure in the auxiliary section due tothe rapid burning caused by the turbulence therein; and

E. causing the combustion products of the auxiliary section to escapethrough the orifice into the main section creating sufficient turbulencetherein to cause substantially total burning within a 60 crank angle.

2. A method according to claim 1 wherein the combustible mixture isignited in the main section and the flame is carried into the auxiliarysection by the combustible mixture being forced therein, the size of theorifice being selected such that the flame will not be quenched by theturbulence generated by the jet passing into the auxiliary section.

3. A method according to claim 1 wherein the combustible mixture isignited in the auxiliary section and the flame is carried into the mainsection by the combustion products forced out of the auxiliary section,the size of the orifice being selected such that the flame will not bequenched by the turbulence generated by the jet passing into the mainsection.

4. A method according to claim 1 wherein the diameter of the orificebetween the main and auxiliary sections is equal to or larger than 1V,,/S,, at cm where 17,, is the thickness of the combustion wave in cm,S is the speed of the combustion wave in cm/sec, V, is the speed cm/secof the jet carrying the flame into the nonignited section and a is thenumerical factor on the order of 1 to 2, the value of which is dependenton the flow conditions around the jet.

5. A method according to claim 1 wherein the volume of the auxiliarysection is between 3 and 15 percent of the total compression volume.

6. The method according to claim 1 wherein the volume of the auxiliarysection is between 8 and 12 per cent of the total compression volume.

7. A method according to claim l.whereir l the volume of the auxiliarysection is typically 10 percent of the compression volume. a

8. A method of operating an internal combustion spark ignition enginehaving at least one cylinder and reciprocating piston therein defining acombustion chamber, said combustion chamber divided into a main andauxiliary section, said auxiliary section being in communication onlywith said main section, there being an orifice between the main andauxiliary section sized to pass a flame ari d promote turbulence suchthat harmful exhaust emissions including CO, NO and unburnedhydrocarbons are substantially reduced during normal operation and suchthat harmful exhaust emissions comprising anti-knock additives aresubstantially eliminated comprising the steps during normal operationfor A. introducing only a very lean combustible mixture having anair-fuel ration of at least 18:1 only to the main section of thecombustion chamber;

B. compressing the combustible mixture in the main section of thecombustion chamber and thereby forcing part of the mixture through theorifice into steps during peak power operation minor, if any, amounts ofanti-knock additives to the main section of the combustion chamber;

B. compressing the combustible mixture in the combustion chamber andthereby forcing a part of the mixture through the orifice in theauxiliary section creating great turbulence therein;

C. igniting the combustible mixture within the combustion chamber;

D. causing a very rapid rise in pressure in the auxiliary section due torapid burning caused by turbulence therein; and

E. causing the combustible products of the auxiliary section to escapethrough the orifice into the main section creating sufficient turbulencetherein to cause substantially total burning within a 30 crank angle.

9. In an internal combustion spark ignition engine that minimizesharmful exhaust emissions including CO, NO and unburned hydrocarbons, atleast one cylinder and reciprocating piston therein defining acombustion chamber, there being only one spark plug per cylinder, meansfor dividing the combustion chamber into the main and auxiliarysections, said auxiliary section being in communication with only saidmain section; said dividing means defining an orifice between thesections, means for introducing a very lean combustible mixture only tothe main section of the combustion chamber, the ratio of the volume ofthe main and auxiliary sections and the size of the orifice selectedsuch that during the compression cycle part of the combustible mixtureof fuel and air rushes into the auxiliary sectioncausing greatturbulence therein and after ignition the combustion products rush outof the auxiliary section into the main section causing turbulencetherein sufficient to provide combustionoi' a very lean air-fuel mixturehaving an air-fuel ratio of at least 18:1 that is substantially totalwithin a 60 crank angle, the size of said orifice further selectedsufficiently large such that the burning jet passed therethrough intothe nonignited section will not be quenched by excessive turbulence.

10. An internal combustion engine according to claim 9 wherein the ratioof the volumes of the main and auxiliary sections and the size of theorifice are further selected such that during peak power operation ofthe engine sufiicient turbulence is created in the main section toprovide combustion of a near stoichiometric air-fuel mixture that issubstantially total within a 30 crank angle.

11. An engine according to claim 9 wherein electrodes of the spark plugare provided in the auxiliary section for causing ignition.

12. An engine according to claim 9 wherein electrodes of the spark plugare provided in the main section for causing ignition.

13. An engine according to claim 9 wherein the diameter of the orificebetween the main and auxiliary sections is equal or larger than ('1V,,)/(S,, (1) cm where 1 is the thickness of the combustion wave in cm,8,, is the speed of the combustion wave in cm/sec, V is the speed cm/secof the jet carrying the flame into the nonignited section and a is anumerical factor on the order of l to 2, the value of which is dependenton the flow conditions around the jet.

14. An engine according to claim 9 wherein the volume of the auxiliarysection is between 3 and 15 percent of the total compression volume.

15. An engine according to claim 9 wherein the volume of the auxiliarysection is between 8 and 12 percent of the total compression chamber.

16. An engine according to claim 9 wherein the volume of the auxiliarysection is typically 10 percent of the compression volume.

UNITED STATES PATENT ()FFICE CERTIFICATE OF CORRECTION Patent No. 3,776, 212 Dated December 4, 1973 InventoflX) Bela Karlovitz It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Under the heading entitled Related U. S.

Application Data, --February 12, l964 should read --February 12, l969-.Column 1 Line 22 This-- should read Their-'. Column 3 Line 36-change---- should read -charge- Column 3 Line 51 -18 cal/cm C secshouldread --cal/cmC sec--. Column 5 Line 6 -psi degree-- should read -psi perdegree-. Column 7 Line 49 heshould read --the-. Column 8 Line 52\--wit-- should read --with--.

Signed and sealed this 16th day of April 197R.

(SEAL) I Attest:

EDWARD I I.FLETGHER,JR. I IIARSHALL- DANN Attesting Officer ICommissioner of Patents USCOMM-DC 60376-P69 w u.s. GOVERNMENT rmujmsOFFICE: nu o-su-su,

F ORM F'O-I 050 (10-69)

1. A method of operating an internal combustion spark ignition enginehaving at least one cylinder and reciprocating piston therein defining acombustion chamber, said combustion chamber divided into main andauxiliary sections, said auxiliary section being in communication onlywith said main section, there being an orifice between the main andauxiliary section sized to pass a flame and promote turbulence such thatthe harmful exhaust emissions including CO, NO and unburned hydrocarbonsare substantially reduced comprising the steps for, A. introducing onlya very lean combustible mixture having an air-fuel ratio of at least18:1 only to the main section of the combustion chamber; B. compressingthe combustible mixture in the main section of the combustion chamberand thereby forcing part of the mixture through the orifice into theauxiliary section creating great turbulence therein; C. igniting thecombustible mixture withiN the combustion chamber from a single ignitionsource: D. causing a very rapid rise in pressure in the auxiliarysection due to the rapid burning caused by the turbulence therein; andE. causing the combustion products of the auxiliary section to escapethrough the orifice into the main section creating sufficient turbulencetherein to cause substantially total burning within a 60* crank angle.2. A method according to claim 1 wherein the combustible mixture isignited in the main section and the flame is carried into the auxiliarysection by the combustible mixture being forced therein, the size of theorifice being selected such that the flame will not be quenched by theturbulence generated by the jet passing into the auxiliary section.
 3. Amethod according to claim 1 wherein the combustible mixture is ignitedin the auxiliary section and the flame is carried into the main sectionby the combustion products forced out of the auxiliary section, the sizeof the orifice being selected such that the flame will not be quenchedby the turbulence generated by the jet passing into the main section. 4.A method according to claim 1 wherein the diameter of the orificebetween the main and auxiliary sections is equal to or larger than eta oVo/Su Alpha cm where eta o is the thickness of the combustion wave incm, Su is the speed of the combustion wave in cm/sec, Vo is the speedcm/sec of the jet carrying the flame into the nonignited section andAlpha is the numerical factor on the order of 1 to 2, the value of whichis dependent on the flow conditions around the jet.
 5. A methodaccording to claim 1 wherein the volume of the auxiliary section isbetween 3 and 15 percent of the total compression volume.
 6. The methodaccording to claim 1 wherein the volume of the auxiliary section isbetween 8 and 12 percent of the total compression volume.
 7. A methodaccording to claim 1 wherein the volume of the auxiliary section istypically 10 percent of the compression volume.
 8. A method of operatingan internal combustion spark ignition engine having at least onecylinder and reciprocating piston therein defining a combustion chamber,said combustion chamber divided into a main and auxiliary section, saidauxiliary section being in communication only with said main section,there being an orifice between the main and auxiliary section sized topass a flame and promote turbulence such that harmful exhaust emissionsincluding CO, NO and unburned hydrocarbons are substantially reducedduring normal operation and such that harmful exhaust emissionscomprising anti-knock additives are substantially eliminated comprisingthe steps during normal operation for A. introducing only a very leancombustible mixture having an air-fuel ration of at least 18:1 only tothe main section of the combustion chamber; B. compressing thecombustible mixture in the main section of the combustion chamber andthereby forcing part of the mixture through the orifice into theauxiliary section creating great turbulence therein; C. igniting thecombustible mixture within the combustion chamber from a single ignitionsource; D. causing a very rapid rise in pressure in the auxiliarysection due to the rapid burning caused by the turbulence therein; andE. causing the combustion products of the auxiliary section to escapethrough the orifice into the main section creating sufficient turbulencetherein to cause substantially total burning within a 60* crank angle,and comprising the steps during peak power operation for A. introducinga combustible mixture having an air-fuel ratio of approximatelystoichiometric and very minor, if any, amounts of anti-knock additivesto the main section of the combustion chamber; B. compressing thecombustible mixture in the combustion chamber and thereby forcing a partof the mixTure through the orifice in the auxiliary section creatinggreat turbulence therein; C. igniting the combustible mixture within thecombustion chamber; D. causing a very rapid rise in pressure in theauxiliary section due to rapid burning caused by turbulence therein; andE. causing the combustible products of the auxiliary section to escapethrough the orifice into the main section creating sufficient turbulencetherein to cause substantially total burning within a 30* crank angle.9. In an internal combustion spark ignition engine that minimizesharmful exhaust emissions including CO, NO and unburned hydrocarbons, atleast one cylinder and reciprocating piston therein defining acombustion chamber, there being only one spark plug per cylinder, meansfor dividing the combustion chamber into the main and auxiliarysections, said auxiliary section being in communication with only saidmain section; said dividing means defining an orifice between thesections, means for introducing a very lean combustible mixture only tothe main section of the combustion chamber, the ratio of the volume ofthe main and auxiliary sections and the size of the orifice selectedsuch that during the compression cycle part of the combustible mixtureof fuel and air rushes into the auxiliary section causing greatturbulence therein and after ignition the combustion products rush outof the auxiliary section into the main section causing turbulencetherein sufficient to provide combustion of a very lean air-fuel mixturehaving an air-fuel ratio of at least 18:1 that is substantially totalwithin a 60* crank angle, the size of said orifice further selectedsufficiently large such that the burning jet passed therethrough intothe nonignited section will not be quenched by excessive turbulence. 10.An internal combustion engine according to claim 9 wherein the ratio ofthe volumes of the main and auxiliary sections and the size of theorifice are further selected such that during peak power operation ofthe engine sufficient turbulence is created in the main section toprovide combustion of a near stoichiometric air-fuel mixture that issubstantially total within a 30* crank angle.
 11. An engine according toclaim 9 wherein electrodes of the spark plug are provided in theauxiliary section for causing ignition.
 12. An engine according to claim9 wherein electrodes of the spark plug are provided in the main sectionfor causing ignition.
 13. An engine according to claim 9 wherein thediameter of the orifice between the main and auxiliary sections is equalor larger than ( eta o Vo)/(Su Alpha ) cm where eta o is the thicknessof the combustion wave in cm, Su is the speed of the combustion wave incm/sec, Vo is the speed cm/sec of the jet carrying the flame into thenonignited section and Alpha is a numerical factor on the order of 1 to2, the value of which is dependent on the flow conditions around thejet.
 14. An engine according to claim 9 wherein the volume of theauxiliary section is between 3 and 15 percent of the total compressionvolume.
 15. An engine according to claim 9 wherein the volume of theauxiliary section is between 8 and 12 percent of the total compressionchamber.
 16. An engine according to claim 9 wherein the volume of theauxiliary section is typically 10 percent of the compression volume.